Novel 3-ethoxycarbonyl-2-ethoxy- and 2-ethoxy-4,9-methanocyclopentacycloundecenes 12 and 13 are synthesized by the reaction of 9-chloro-1,6-methano[11]annulen-8-one 8, a 10π-electron vinylogue of 2-chlorotropone, with 2-ethoxy-3-(ethoxycarbonyl)prop-2-enylidene- and 2-ethoxyprop-2-enylidenetriphenylphosphorane, 7a and 7b, respectively. The reaction pathways involve a Michael-type addition of phosphoranes 7a,b onto ketone 8, subsequent proton migration regenerating the phosphorane moiety, which undergoes intramolecular Wittig reaction, and aromatization, eliminating HCl. The 1H NMR spectra show that compounds 12 and 13 are aromatic molecules having a diatropic 14-electron cyclic π system. The UV–visible absorption spectra of compounds 12 and 13 exhibit extended cyclic conjugation of the aromatic perimeter according to a bathochromic shift of the longest absorption maxima as compared to those of the related azulene derivatives having the same substituents. In addition, the first example of an aromatic substitution reaction of the methanocyclopentacycloundecene ring system has been studied, and shows that the compounds 12 and 13, like azulene, undergo trifluoroacetylation under exceptionally mild conditions and exhibit the same site-selectivity as does azulene. The electrochemical properties of compounds 12 and 13 as well as the related azulene derivatives are also analyzed and discussed on the basis of MNDO calculations.
新型3-乙氧基羰基-2-乙氧基-和2-乙氧基-4,9-亚甲基环五环
十一碳烯12和13是通过9-
氯-1,6-亚甲基[11]annulen-8-one 8、10π- 2-
氯代酮与2-乙氧基-3-(乙氧基羰基)丙-2-烯叉基-和2-乙氧基丙-2-烯叉基
三苯基膦的电子
乙烯系,分别为7a和7b。反应途径包括将正膦 7a,b 迈克尔型加成到酮 8 上,随后质子迁移再生正膦部分,该部分经历分子内 Wittig 反应,以及芳构化,消除 HCl。 1H NMR谱表明化合物12和13是具有双异性14电子环状π体系的芳香族分子。与具有相同取代基的相关甘菊环衍
生物相比,化合物 12 和 13 的紫外-可见吸收光谱根据最长吸收最大值的红移表现出芳香族周长的扩展循环共轭。此外,还研究了亚甲基环五环
十一碳烯环系的芳香族取代反应的第一个实例,结果表明化合物12和13与甘菊环一样,在极其温和的条件下进行三
氟乙酰化,并表现出与甘菊环相同的位点选择性。基于MNDO计算,对化合物12和13以及相关甘菊环衍
生物的电
化学性质进行了分析和讨论。